Charging System Circuit Description. Chevrolet PJJ 2000

For 1990-2009 cars

The generator provides DC voltage to operate the vehicle's electrical system and to charge the battery. A magnetic field is created when current flows through the rotor windings. The rotor is belt driven by the engine creating an AC voltage as this field rotates within the stator windings. The AC voltage is converted to DC voltage by the rectifier bridge and is then supplied to the electrical system at the generator battery terminal.

When the engine is running, the generator turn-on signal is sent to the generator from the PCM, turning on the regulator. The generator's voltage regulator controls the current flow to the rotor, thereby controlling the generator output voltage. The rotor current is proportional to an electrical pulse width modulated voltage supplied by the regulator. When the engine is started, the regulator senses generator rotation by detecting AC voltage at the stator through an internal wire. Once the engine is running, the regulator varies the field current by controlling the pulse width. This regulates the generator's output voltage for proper battery charging and electrical system operation. The generator F terminal is connected internally to the voltage regulator and externally to the PCM. When the voltage regulator detects a charging system problem, it grounds this circuit to signal the PCM that a problem exists.

When the ignition switch is turned to RUN, the charge indicator turns ON for a few seconds (bulb check), then turns OFF. The powertrain control module (PCM) commands the charge indicator ON or OFF by sending a Class 2 serial data message to the instrument panel cluster.